Organic Light-Emitting Diode (OLED) display device has become a very important display technology in the field of flat panel display, due to its advantages such as small thickness, light weight, wide viewing angle, self-luminescence, capable of continuously adjusting wavelengths of light, low cost, rapid response, low power consumption, wide operation temperature range, simple production process, high luminescence efficiency, suitable for flexible display and the like.
Substances such as water vapor and oxygen in the air have a great influence on the service life of OLED in the OLED display device. Cathode of the OLED is typically made of metals such as aluminum, magnesium and calcium, and these metals are apt to react with the water vapor and oxygen permeated into the OLED display device because of their relatively active chemical nature. In addition, the water vapor and oxygen will also react with a hole transporting layer and an electron transporting layer of the OLED, and these reactions will cause failure of the OLED. Therefore, an effective encapsulation of the OLED display device to sufficiently separate respective functional layers of the OLED from the water vapor, oxygen and other substances in the atmosphere can greatly prolong the service life of the OLED and the service life of the OLED display device.
Encapsulation method of the OLED display device typically comprises two types: substrate encapsulation and thin film encapsulation (TFE). The substrate encapsulation refers to filling a glue film between a display substrate formed with the OLED and an encapsulation substrate, so that the glue film after being cured allows an airtight space to be formed between the display substrate and the encapsulation substrate. The thin film encapsulation refers to covering the surface of the OLED with a thin film encapsulation layer consisting of an inorganic thin film and an organic thin film, so that it is difficult for the water and oxygen to penetrate into the OLED.
FIG. 1 is a schematic cross-section view illustrating an OLED display device using thin film encapsulation. As shown in FIG. 1, the OLED display device comprises the thin film encapsulation layer covering the OLED (comprising a first electrode 110, a second electrode 113, and a light-emitting layer 112 provided therebetween), the thin film encapsulation layer comprises a plurality of first thin film encapsulation layers 130-1 and a plurality of second thin film encapsulation layers 130-2 which are alternately stacked. The first thin film encapsulation layer 130-1 is formed to be larger than the second thin film encapsulation layer 130-2 and envelops edges of the second thin film encapsulation layer 130-2, in order to limit prevent the water vapor and oxygen in the air entering into the OLED from the edges of the thin film encapsulation layer. In this case, it is necessary to respectively form the first thin film encapsulation layer 130-1 and the second thin film encapsulation layer 130-2 by using two different mask plates. Further, according to one technique, a plurality of thin film encapsulation layers with gradually increasing sizes are sequentially formed on the OLED and an upper thin film encapsulation layer envelops edges of a lower thin film encapsulation layer to better limit or prevent the water vapor and oxygen in the air entering into the OLED from the edges of the thin film encapsulation layers. In this case, it is necessary to respectively form the plurality of thin film encapsulation layers by using a plurality of different mask plates.
As can be seen above, it is necessary to implement the thin film encapsulation by using at least two mask plates and to frequently replace the mask plates, which will increase production cost and render the production process complicated.